THE SENSITIZING SUBSTANCE. 
We ventured the suggestion in our former publication that the 
substance that sensitizes the guinea pig is the same as that which 
j later poisons it; profound chemical changes perhaps in the central 
li nerve cells, are probably produced b}^ the first injection. Our sub- 
sequent work has produced nothing to alter this working h}"pothesis. 
Vaughan^ advances the theoiy that the first injection of the 
strange proteid is broken up into components, one of which is toxic, 
I but that the animal is not poisoned because this breaking up takes 
place slowly. The cells, however, learn from this lesson how to 
break up the complex molecule, so that when more of the strange 
proteid is introduced at the second injection it is violently rent 
; asunder, quickly liberating large quantities of the toxic principle of 
; the complex molecule. 
I Vaughan and Wheeler* have elaborated this explanation by fur- 
j ther studies upon egg-white and bacterial proteids split into poison- 
j ous and nonpoisonous portions. These authors believe that when 
II egg-white, or the nonpoisonous portion of egg-white, is injected into 
i a fresh animal certain cells of the body are so influenced that they 
I elaborate a new ferment, which, in the form of zymogen, remains in 
i the cell until activated by the second injection, when it is set free and 
splits up the egg-white in a manner similar to that used b}^ Vaughan 
1 in the laboratory. Vaughan and Wheeler believe that the efl'ect 
.,| induced in the animal is the same as that caused b}- the poisonous por- 
■ ji tions of egg-white as they have split it up in the retort. 
j Currie^ suggests that the first injection of serum results after an 
|| interval in the formation of an antibody. When the second injection 
iij of serum is given, after at least ten days from the first, the antibod}^- 
producing substance of the second injection of serum and theantibod}^ 
,,! Vaughan, V. C. : Discussion of “Hypersusceptibility,” by M. J. Rosenau and 
j| J. F. Anderson. Journ. Am. Med. Assn., Vol. 47, No. 13, Sept. 29, 1906, p. 1009. 
I ^Vaughan, Victor C., and Wheeler, May: Effects of egg-white and its split 
i products upon animals. A study of susceptibility and immunity. Abstract of 
I I papers to be read at twenty -second annual meeting of Assn. Am. Physicians, Wash- 
I’i ington, May 7-9, 1907, p. 9. 
I Currie, J. R. : On the supersensitation of persons suffering from diphtheria by 
1 repeated injections of horse serum. Journ. Hygiene, Vol. 7, No. 1, Jan., 1907, pp. 
■ 35-60. 
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